Differential clutch released by hydraulic brake application

ABSTRACT

A hydraulic release for a differential lock releasing in response to actuation of a relay valve having a hydraulic actuator in the hydraulic brake system for each of the rear wheels.

United States Patent Schett Feb. 15, 1972 s41 DIFFERENTIAL CLUTCHRELEASED 3,446,320 5/1969 Schott ..192/4 A BY HYDRAULIC BRAKEAPPLICATION 3,463,277 8/1969 AllOfi et al ..192/4 A 3,467,212 9/1969 DO.;..74/710.5 x [72] Invent New Beflm 3,498,427 3/1970 Bingley 192/4 A x[73] Assignee: Allis Chalmers Manufacturing Company,

' M'lwaukeei Wm Primary Examiner-Benjamin W. Wyche 22 pi J 1 1970Attorney-Arthur L. Nelson; Robert B. Benson and Kenneth C. McKivett 211A 1. NO.; 3,370

ABSTRACT E A hydraulic release for a differential lock releasing inresponse [58 Field of Search 192/4, 4 A, 13; 74/7105 actuatiofi of arelay valve having a hydraulic actuator Y hydraulic brake system foreach of the rear wheels. [56] ems CM 10 Claims, 1 Drawing Figure UNITEDSTATES PATENTS 3,292,720 12/1966 Harvey "74/7105 x This inventionrelates to a differential lock and more particularly to the hydraulicactuator connected to the hydraulic systems for each of the rear wheelbrakes which releases the differential lock by actuation of either orboth of the rear wheel brakes.

Conventional tractors employ a differential in the final drive systemfor driving the rear axles. The differential permits either wheel torotate at a different rate than the other wheel which permits turning ofthe vehicle. While the differential action on the rear wheels isnecessary in turning, it is also desirable to lock the differential sothat both the right and the lefthand final drive axles turn at aconstant rate when the vehicle is traveling straight ahead. With thedifferential locked, both rear wheels turn in unison so that a variabletraction of the rear wheels will not cause slippage of the one wheel andloss of the draft to the drawbar. I

The control operating the differential lock shown herein has a manualmeans to engage the lock. The differential lock control can be manuallyengaged and automatically disengaged. Usually when a tractor is turnedto the right or left, one of the brakes is usually applied. An automaticrelease for releasing the differential lock at a time when the vehicleis about to be turned to the right and to the left is desirable andaccordingly, the use of the hydraulic brake pressure to disengage thedifferential lock is convenient. There are however, circumstances whenboth of the rear wheel brakes might be applied and it is desirable torelease the differential lock.

Accordingly this invention provides a means whereby the differentiallock can be released by actuation of either one or both of the rearwheel brakes. A hydraulic actuator for a relay valve controls the flowof pressurized fluid to the control valve which controls the flow ofpressurized fluid to the differential lock. The actuator for the relayvalve is in the hydraulic rear wheel brake circuit which providesaconvenient means for releasing the differential clutch on thedifferential between the rear wheels.

It is an object of this invention to provide hydraulic means for releasefor the differential lock in response to actuation of either rear wheelbrake or both the rear wheel brakes.

It is another object of this invention to-provide a differential lockrelease controlled by a relay valve having an actuator in the hydrauliccircuitfor each ofthe rear wheel brakes.

It is a further object of this invention to provide a differential lockrelease having a relay valve with an actuator in the hydraulic circuitfor each of the rear wheel brakes whereby the relay valve permits theflow of pressurized fluid to the control valve actuator. The controlvalve moves to prevent flow of pressurized fluid to the differentialclutch and thereby permits the rear axles connected to the differentialto rotate freely relative to each other.

The objects of this invention are accomplished by providing ahydraulically actuated clutch in the differential. The clutch has ahydraulic actuator which engages the clutch in response to admission ofpressurized fluid in the hydraulic actuator. A source of pressurizedfluid supplies pressurized fluid to the actuator of the differentialclutch through a control valve which controls the flow of pressurizedfluid. A relay valve has an actuator in each of the brake circuitsbiasing the relay valve to a position to divert pressurized fluid to theactuator of the control valve which in turn closes communication betweenthe source of pressurized fluid to the clutch actuator and vents theclutch actuator to sump for release of the differential.

Hydraulic operating means are provided in the actuator for the relayvalve in which a single plunger is connected to each of the brakecircuits. Accordingly, when either of the hydraulic brake circuits ispressurized, the relay valve diverts pressurized fluid to the actuatorfor the control valve and thereby releasing the differential look. whenhydraulic fluid pressurizes both of the plungers the result is the same,the differential clutch is released. I

The preferred embodiment of this invention will be described in thefollowing paragraphs and illustrated in the attached drawing.

The drawing illustrates a hydraulically actuated differential lock andthe hydraulically actuated rear wheel brakes.

Referring to the drawing, the pump 1 receives pressurized fluid 2 fromthe reservoir 3. The conduit 4 transmits hydraulic fluid to the pump.The pump 1 discharges pressurized fluid into the conduit 5 connected tothe pressure-limiting valve 6, which is normally closed, permits'thedischarge of pressurized fluid through the line 7 to the reservoir 3when a predetermined pressure is reached in the conduit 5.

The conduit 5 is connected through conduit 8 to the righthand brakevalve 9 and the left-hand brake valve 10. The brake lever 11 operatesthe right-hand brake while the brake lever 12 operates the left-handbrake. The link 13 connects the brake lever 11 to the spool 14 whichmoves reciprocally within the brake valve housing 15. The pressurizedfluid passes through the conduit 8 into the pressure chamber 16 of valvehousing 15. As the spool 14 is moved upwardly the conduit 8 is connectedto the chamber 17 and conduit 18 permitting the flow of pressurizedfluid into the passage 19.

When the brake lever 11 is released the spring 20 and 90 biases thespool 14 downwardly whereby the spool releases the pressure from thechamber 17 through conduits 83 and 21. The return conduits 83 and 21 arethen in communication with the chamber 17 and the reservoir 3.

The left-hand lever 12 is connected by a link 22 to the spool 23. Whenthe lever 12 is depressed the spool 23 moves upwardly permitting theflow of pressurized fluid from the pressure chamber 16 into the chamber24'which is connected by conduit 25 to the passage 26. When the lever 12is released the spring 27 and 91 biases the spool 23 downwardly closingcommunication between the chamber 16 and the conduit 25. Conduit 84 and21 are then in communication with chamber 24 and reservoir 3. Adescription of the clutch in the differential will be describedsubsequently. The left-hand wheel brake 28 comprises brake housing 29defining the hydraulic wheel cylinder receiving the hydraulic wheelpiston 30. The hydraulic wheel piston 30 compresses the disc stack 31which has alternate brake discs connected to the'housing and the brakehub 32 which is splined to the rear axle 33. 7

Similarly the right-hand brake 34 comprises abrake housing 35 defining awheel cylinder receiving the piston 36 which compresses the disc stack37 to operate the right-hand rear wheel brake. The disc stack includesalternate interleaved brake discs alternately connected to the brakehousing 35, and the brake hub 38 which is splined to the right-hand rearaxle The right-hand rear aide 39 and the left-hand rear axle 33 areconnected to the differential 40 comprising the differential gears 41,42, 43 and 44. The differential housing 45 is connected to the ring gear46 which is driven by the pinion 47. The ring gear 46 is splined to aplurality of clutch discs 48 while the pinion 44 is splined to aplurality of alternate clutch discs 49. The hydraulic actuator forclutch 50 includes the piston 51 which defines the pressurizing chamber52 which receives pressurized fluid from the conduit 53. The conduit 53is connected to a valve means 54.

The valve means 54 consists of a control spool 55 reciprocally mountedwithin the housing 56 biased to the left-hand position by the spring 57.The detent 58 received in the annular recess 59 retains the position ofthe spool 55 as shown in response to the biasing force of the detentspring 60. The manual lever 61 manually reciprocat'es the spool 55.andprovides a means of positioning the spool in the position as shown.

The conduit 5 is connected to valve means 54 and supplies pressurizedfluid to the chamber 62 which is in turn in communication with thepassage 63 and conduit 53 in the position as shown. In this positionpressurized fluid is supplied to the pressurizing chamber 52 of theactuator 51 and the differential is locked. Y

The spool 55 defines a control valve 64 which controls the flow ofpressurized fluid from the chamber 62. When the spool 55 is moved to itsleft-hand position the washer 66 engages the shoulder 67 and the land 68closes communication between the conduit 5 and passage 63. Chamber 92and 63 are connected through conduit 21 to the reservoir 3. Shifting ofthe spool 55 to this position is accomplished by supplying pressurizedfluid to the chamber 69.

The plunger 70 is received in the cylindrical opening 71. The plunger 70is formed with a slot 72 in communication with the passage 26 whichpermits the flow of pressurized fluid through the slot 72 to the conduit73 which in turn pressurizes fluid in the conduit 73 and actuates thepiston 30 for the lefthand hydraulic brake 28. Pressurized fluid alsobiases the plunger 70 to the right-hand position which in turn moves theplunger 77 and causing the land 78 to permit communication between thepassage 63 and the chamber 69. Pressurized fluid in the chamber 69 inturn will cause the spool 55 to move to the left-hand direction closingcommunication between conduit 5 and conduit 53 and opening communicationbetween chamber 63 and 92 which is connected to reservoir 3 forreleasing the differential clutch.

Similarly when the right-hand brake 34 is actuated, pressurized fluidflows into the chamber 80 which in turn biases the plunger 70 in theleft-hand direction and the plunger 77 in the right-hand direction. Asthe plunger 77 moves in the righthand direction pressurized fluid ispermitted to flow from the passage 63 to the chamber 69 which in turnbiases the spool 55 to the left-hand direction closing communicationbetween conduit 5 and conduit 53 and opening communication betweenchamber 63 and 92 and reservoir 3 which in turn releases thedifferential clutch.

When both of the brake levers 11 and 12 are activated, pressurized fluidflows into the chamber 80 and into the chamber 82 and the pressurizedfluid will bias the spool 77 in the right-hand direction placingcommunication between the passage 63 and the chamber 69. Pressurizedfluid in the chamber 69 biases spool 55 in the left-hand direction andcloses communication between the passage conduit 5 and conduit 53 andopening communication between chamber 63 and 92 which releases thedifferential 50. a

The operation of this device will be described in the followingparagraphs.

The pump 1 supplies pressurized fluid to the brake valves 9 and 10 toactuate the brakes 34 and 28 respectively. The pump 1 also suppliespressurized fluid to the valve means 54 which controls the flow ofpressurized fluid to the actuator for differential clutch 50. When thecontrol spool 55 for the differential valve isin the position shown,pressurized fluid flows from the pump through the conduit 5 and conduit53 to actuate the clutch 50 for the differential 40. Chamber 69 isconnected to conduit 21 and reservoir 3. in this position, the rearaxles 33 and 39 rotate synchronously.

When the left-hand brake lever 12 is depressed the pressurized fluidfrom the pump 1 flows through chamber 16, valve 10, conduit 25, slot 72and conduit 73 to engage the lefthand brake 28. Pressurized fluid in theslot 72 of the plunger 70 biases the plunger in the right-hand directioncarrying the plunger 77 closing communication between chamber 69,conduit 21, and reservoir 3 and placing communication between thepassage 63 and the chamber 69. Pressurized fluid in chamber 69 biasesthe spool 55 in the left-hand direction severing communication betweenthe conduit 5 and the conduit 53 and opening communication betweenchambers 63, 92, conduit 21 and reservoir 3. This in turn releases theclutch 50 of the differential 40.

When the right-hand brake level 1 l is depressed pressurized fluid fromthe pump 1 flows through a valve 9 to the chamber 17 through conduit 18and 19 with pressurized fluid actuating the right-hand brake 34. Thepressurized fluid in passage 19 also goes into the chamber 80 which inturn biases the plunger 77 in the right-hand position. This closes ofichamber 69 from reservoir 3 and places communication between the passage63 and the chamber 69 biasing the spool 55 in the left-hand directionsevering communication between the conduit 5 and conduit 53 placingcommunication between chambers 92, 63 and reservoir 3. Accordingly, thedifferential clutch 50 is released.

When brake levers 11 and 12 are depressed, pressurized fluid flowsthrough the same conduits as previously described actuating both theright and left-hand brakes 34 and 28 and also flows through the slot 72in plunger'70 and into chamber which in turn biases the plunger 77 tothe right-hand position severing communication between chamber 69 andreservoir 3 placing communication between the passage 63 and the chamber69 which in turn shifts the spool 55 to the left-hand direction inresponse to the pressure of the fluid thereby closing communicationbetween conduits 5 and 53 and opening chambers 63 and 92 to reservoir 3.This in turn releases the differential clutch for the differential 40.

To reposition the spool 55, the manual lever 61 is moved downwardlyuntil the detent 58 drops in the annular recess 59. The spool 55 is thenretained in this position until it is released automatically in responseto pressurized fluid operating on the actuator for the spool 55.

I claim:

1. A vehicle having hydraulic brakes and a differential drive meansconnecting two final drive shafts, a hydraulic system including a sourceof pressurized fluid, a hydraulically actuated clutch locking saiddifferential drive means for synchronously rotating said final driveshafts, a hydraulic control valve means including manual meanscontrolling the flow of pressurized fluid from said source ofpressurized fluid to said hydraulically actuated clutch and a hydraulicoperating means biasing said valve to interrupting communication betweensaid source of pressurized fluid and said hydraulically actuated clutch,a hydraulic brake circuit having brakes for brakingeach of said finaldrive shafts, a hydraulic relay valve connected through said controlvalve in said hydraulic system connected between said source ofpressurized fluid said hydraulically actuated clutch and said hydraulicoperating means of said control valve including actuating meanshydraulically in communication with said hydraulic brake circuit foroperating said relay valve means, a spring normally biasing said relayvalve in one direction to a first position for directing flow ofpressurized fluid from said source of pressurized fluid to saidhydraulically actuated clutch, said relay valve comprising a hydraulicactuator in communication with one of said hydraulic brakes, a secondhydraulic actuator in communication with the other of said hydraulicbrakes, said hydraulic actuators both moving said relay valve in asecond direction opposite to said first direction to a second positionagainst the force of said spring means for directing the flow ofpressurized flow from said source of pressurized fluid to said hydraulicoperating means on said control valve means to close said control valvemeans and deenergize said clutch on said differential drive means tothereby deenergize said hydraulically actuated clutch in response toactuation of one or both of said hydraulic brakes.

2. In a vehicle having hydraulic brakes and a differential drive meansconnecting two final drive shafts as set forth in claim 1, wherein saidhydraulic system includes a hydraulic actuator connected to said firstbrake and said second brake.

positioned in tandem for operation of said relay valve.

3. In a vehicle having hydraulic brakes and a differential drive meansconnectingtwo final drive shafts as set forth in claim 1, wherein saidhydraulic system includes a single source of pressurized fluid foractuating said brakes and said differential clutch.

4. In a vehicle having hydraulic brakes and a differential drive meansconnecting two final drive shafts as set forth in claim 1, wherein saidhydraulic brake circuit includes said hydraulic actuators for said relayvalve wherein said actuators define passage means accommodating the flowof pressurized fluid through said actuators to said first and secondbrake for actuation of said brakes.

5. ln a vehicle having hydraulic brakes and a differential drive meansconnecting two final drive shafts as set forth in claim I, wherein saidhydraulic system includes a reservoir, said relay valve includes aspringnormally biasing said relay valve means to normally connect saidhydraulic actuator means of said control valve to said reservoir whensaid hydraulic clutch is actuated.

6. In a vehicle having hydraulic brakes and a differential drive meansconnecting two final drive shafts as set forth in claim 1, wherein saidcontrol valve includes a spring normally biasing said control valvetoward a closed position, a detent mechanism normally retaining saidcontrol valve in an open position to provide energization of saiddifferential clutch.

7. In a vehicle having hydraulic brakes and a differential drive meansconnecting two final drive shafts as set forth in claim 1, wherein saidhydraulic system includes a control valve including low-pressure passagemeans normally connecting the hydraulic operating means of said controlvalve to a low-pressure reservoir, said relay valve closing saidlow-pressure passage means and placing communication between said sourceof pressurized fluid and said hydraulic operating means i of saidcontrol valve to thereby close said control valve when said brakes areactuated.

8; In a vehicle having hydraulic brakes and a differential drive meansconnecting two final drive shafts as set forth in claim 1, wherein saidhydraulic system includes a spring normally biasing said control valvetoward a closed position to thereby retain said control valve in aclosed position in response to hydraulic actuation of said control valvewhen said brakes are actuated.

9. In a vehicle having hydraulic brakes and a differential drive meansconnecting two final drive shafts as set forth in claim 1, wherein saidhydraulic system includes said hydraulic actuators for said relay valvemeans comprising a plunger defining a chamber connected to one of saidbrakes, a second plunger and said first plunger defining a secondchamber connected to the other of said brakes wherein said secondplunger disengages from said first plunger when said other brake andboth of said brakes are actuated to operate said relay valve means andrelease said differential clutch.

10. In a vehicle having hydraulic brakes and a differential drive meansconnecting two final drive shafts as set forth in claim 1, wherein saidactuators for said relay valve comprise a first plunger defining achamber connected to one brake, a second plunger defining a secondchamber connected to the the other brake with said second plungerengaging said first plunger when said one of said brakes is actuated.

1. A vehicle having hydraulic brakes and a differential drive meansconnecting two final drive shafts, a hydraulic system including a sourceof pressurized fluid, a hydraulically actuated clutch locking saiddifferential drive means for synchronously rotating said final driveshafts, a hydraulic control valve means including manual meanscontrolling the flow of pressurized fluid from said source ofpressurized fluid to said hydraulically actuated clutch and a hydraulicoperating means biasing said valve to interrupting communication betweensaid source of pressurized fluid and said hydraulically actuated clutch,a hydraulic brake circuit having brakes for braking each of said finaldrive shafts, a hydraulic relay valve connected through said controlvalve in said hydraulic system connected between said source ofpressurized fluid said hydraulically actuated clutch and said hydraulicoperating means of said control valve including actuating meanshydraulically in communication with said hydraulic brake circuit foroperating said relay valve means, a spring normally biasing said relayvalve in one direction to a first position for directing flow ofpressurized fluid from said source of pressurized fluid to saidhydraulically actuated clutch, said relay valve comprising a hydraulicactuator in communication with one of said hydraulic brakes, a secondhydraulic actuator in communication with the other of said Hydraulicbrakes, said hydraulic actuators both moving said relay valve in asecond direction opposite to said first direction to a second positionagainst the force of said spring means for directing the flow ofpressurized flow from said source of pressurized fluid to said hydraulicoperating means on said control valve means to close said control valvemeans and deenergize said clutch on said differential drive means tothereby deenergize said hydraulically actuated clutch in response toactuation of one or both of said hydraulic brakes.
 2. In a vehiclehaving hydraulic brakes and a differential drive means connecting twofinal drive shafts as set forth in claim 1, wherein said hydraulicsystem includes a hydraulic actuator connected to said first brake andsaid second brake positioned in tandem for operation of said relayvalve.
 3. In a vehicle having hydraulic brakes and a differential drivemeans connecting two final drive shafts as set forth in claim 1, whereinsaid hydraulic system includes a single source of pressurized fluid foractuating said brakes and said differential clutch.
 4. In a vehiclehaving hydraulic brakes and a differential drive means connecting twofinal drive shafts as set forth in claim 1, wherein said hydraulic brakecircuit includes said hydraulic actuators for said relay valve whereinsaid actuators define passage means accommodating the flow ofpressurized fluid through said actuators to said first and second brakefor actuation of said brakes.
 5. In a vehicle having hydraulic brakesand a differential drive means connecting two final drive shafts as setforth in claim 1, wherein said hydraulic system includes a reservoir,said relay valve includes a spring normally biasing said relay valvemeans to normally connect said hydraulic actuator means of said controlvalve to said reservoir when said hydraulic clutch is actuated.
 6. In avehicle having hydraulic brakes and a differential drive meansconnecting two final drive shafts as set forth in claim 1, wherein saidcontrol valve includes a spring normally biasing said control valvetoward a closed position, a detent mechanism normally retaining saidcontrol valve in an open position to provide energization of saiddifferential clutch.
 7. In a vehicle having hydraulic brakes and adifferential drive means connecting two final drive shafts as set forthin claim 1, wherein said hydraulic system includes a control valveincluding low-pressure passage means normally connecting the hydraulicoperating means of said control valve to a low-pressure reservoir, saidrelay valve closing said low-pressure passage means and placingcommunication between said source of pressurized fluid and saidhydraulic operating means of said control valve to thereby close saidcontrol valve when said brakes are actuated.
 8. In a vehicle havinghydraulic brakes and a differential drive means connecting two finaldrive shafts as set forth in claim 1, wherein said hydraulic systemincludes a spring normally biasing said control valve toward a closedposition to thereby retain said control valve in a closed position inresponse to hydraulic actuation of said control valve when said brakesare actuated.
 9. In a vehicle having hydraulic brakes and a differentialdrive means connecting two final drive shafts as set forth in claim 1,wherein said hydraulic system includes said hydraulic actuators for saidrelay valve means comprising a plunger defining a chamber connected toone of said brakes, a second plunger and said first plunger defining asecond chamber connected to the other of said brakes wherein said secondplunger disengages from said first plunger when said other brake andboth of said brakes are actuated to operate said relay valve means andrelease said differential clutch.
 10. In a vehicle having hydraulicbrakes and a differential drive means connecting two final drive shaftsas set forth in claim 1, wherein said actuators for said relay valvecomprise a first plunger defining a chamber connectEd to one brake, asecond plunger defining a second chamber connected to the the otherbrake with said second plunger engaging said first plunger when said oneof said brakes is actuated.